The presently disclosed embodiments relate to testing a device under test—DUT—by performing a signal analysis of a test signal received from the DUT.
For testing a DUT, a data analyzer might be connected to the DUT via a test head. The test head provides an electrical contact to an output of the DUT, captures a test signal from the output, and transmits the captured test signal to an analyzing instrument for further processing. Due to specific requirements of different kinds of data analyzers, usually different test heads are used for different kinds of test instruments and corresponding measurements are typically carried out independently in order to avoid cross disturbances.
Examples for such kinds of test instruments might be represented by a sampling oscilloscope and a BERT. The sampling oscilloscope takes a plurality of analog samples of a received signal for e.g. exactly displaying the waveform of the signal. The analog sample rate might be relatively low with respect to the data rate, whereby the samples or sample values show a high accuracy. By varying the sampling time with respect to the clock pattern and repetitively sampling the signal, the waveform of the signal can be derived. A capturing circuit of a sampling oscilloscope might therefore be optimized for an exact, but slow sampling of periodic signals. Such slow sampling technique is also known as undersampling. An example for a measurement instrument with a sampling oscilloscope is the Agilent 86100C Infiniium digital communication analyzer provided by the applicant Agilent Technologies.
A BERT might be regarded as a fast digital signal analyzer e.g. for determining a logical correctness of the test signal. Thereto, the BERT performs a digital comparison of the test signal with a defined threshold and samples the comparison result typically at the bit rate of the test signal, and determines bit error ratio (BER) values indicative of a ratio of erroneous bits to an overall number of bits. Thus, a capturing circuit for a BERT should be adapted for fast digital sampling, typically at the bit rate of the test signal. Examples for such instruments are serial BERTs of the Agilent N4900 Serial BERT Series, and parallel BERT's based on the Agilent ParBERT 81250 platform, both provided by the applicant Agilent Technologies.